Field of the Invention
The present invention relates to a honeycomb body configuration including a housing, a honeycomb body disposed in the housing, and an intermediate layer containing a plurality of layer portions and surrounding the honeycomb body in the housing. Such configurations are used in particular in exhaust gas cleaning systems of motor vehicles, especially for catalytic converters with ceramic honeycomb bodies. The invention also relates to a sandwich structure in particular for a honeycomb body configuration.
German Utility Model GM 80 19 813 U1 already discloses a holder for ceramic honeycomb bodies, in which the honeycomb body is encased in a so-called swell mat and is disposed in a metal housing. The swell mat is capable of swelling to fill up cavities which occur due to different performance characteristics on the part of the housing and the honeycomb body and due to manufacturing tolerances, and can thus ensure a secure support effect over a long period of operation. Swell mats generally contain small pieces of mica which absorb water and in so doing expand, if there is space available in their surroundings. In order to stabilize such swell mats, the utility model proposes integrating a corrugated knitted wire mat into the swell mat. In order to protect the swell mat from being eroded at the ends of the honeycomb body, gas sealing rings are to be provided at the ends of the honeycomb body to cover over a gap which is filled by the swell mat.
Honeycomb bodies in exhaust systems heat up during operation to a temperature of 900xc2x0 C. and more and components disposed in the proximity of the honeycomb body configuration are to be protected from that high temperature. It is therefore also known to provide a thermally insulating intermediate layer between the housing and the honeycomb body.
That thermally insulating layer can be a layer of air which, by virtue of low levels of heat conduction and heat convection properties of the air, insulates the housing from the high temperatures which occur in the honeycomb body during use of the honeycomb body configuration.
Alternatively or in addition to the insulation afforded by the air layer, it is known to provide an intermediate layer which is formed of a ceramic material. That also involves thermal insulation for the housing from the honeycomb body by virtue of low heat conduction and heat convection properties of the ceramic materials being used. The above-mentioned swell mats for holding honeycomb bodies give off water at very high ambient temperatures of, for example, above 800xc2x0 C. and in so doing shrink. The honeycomb body can therefore become loose in the housing. Swell mats must be thermally insulated in relation to the honeycomb body in certain heavily loaded honeycomb body configurations. For that purpose, it is already known for the honeycomb body to be initially provided with a thermal insulation and only then to be enclosed with a swell mat.
However, at temperatures above about 600xc2x0 C. heat transmission occurs not only by heat conduction and heat convection but also, to an increasing degree with temperature, by heat radiation. Nevertheless, the above-described thermal insulations which are known from the state of the art, as well as swell mats, only provide little insulation effect in relation thereto.
A further disadvantage of known honeycomb body configurations is that the insulating intermediate layers which are disposed between the housing and the honeycomb body are eroded by hot pulsating exhaust gases in the region of the ends of the honeycomb body configuration. Even a ceramic intermediate layer which in itself is highly abrasion-resistant is abraded by virtue of the pulsating exhaust gas flow in the course of operation. In that way the thermal insulation between the honeycomb body and the housing is disadvantageously damaged or destroyed in the course of the period of operation of the honeycomb body configuration. That involves damage and possibly even destruction of the entire honeycomb body configuration.
It is accordingly an object of the invention to provide a honeycomb body configuration with an intermediate layer containing at least one metal layer and a sandwich structure in particular for a honeycomb body configuration, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, in which the honeycomb body configuration reduces heat transmission through heat radiation from the honeycomb body to a housing or a swell mat and preferably also prevents or at least reduces erosion of the intermediate layer and in which the sandwich structure permits such a honeycomb body configuration to be easily produced.
With the foregoing and other objects in view there is provided, in accordance with the invention, a honeycomb body configuration, comprising a housing; a honeycomb body disposed in the housing; and an intermediate layer surrounding the honeycomb body in the housing, the intermediate layer having a plurality of layer portions including at least one metal sheet and at least one layer of ceramic material.
With the objects of the invention in view, there is also provided a sandwich structure, in particular for a honeycomb body configuration, comprising at least one metal sheet; and a ceramic layer of thermally insulating fiber material joined to the at least one metal sheet.
By virtue of the fact that in accordance with the invention the intermediate layer contains a plurality of layer portions which include at least one metal foil or sheet, heat transmission from the honeycomb body to the housing through the use of heat radiation is advantageously reduced. The honeycomb body configuration also has good thermal insulating properties in terms of heat conduction and heat convection since in accordance with the invention there are provided a plurality of layer portions which also includes at least one layer of ceramic material. That applies in particular when the ceramic material involves a very low level of heat conductivity.
In accordance with another feature of the invention, any cavities which remain in the honeycomb body configuration between the housing and the honeycomb body upon manufacture thereof or which are formed in the course of operation are advantageously closed if at least one of the layer portions of ceramic material is a swell mat which, upon absorbing water, closes cavities adjacent thereto by swelling. That provides that the honeycomb body is durably and firmly held in position.
In accordance with a further feature of the invention, an embodiment of the intermediate layer which is advantageous from the point of view of production procedure is also afforded by the fact that a layer portion in the form of a metal sheet makes it possible for the honeycomb body configuration to be produced in a simple manner, in particular by winding or coiling. In particular, if the at least one metal sheet and at least one ceramic layer are joined to form a sandwich structure, the intermediate layer can be wound in the peripheral direction around the honeycomb body in a simple procedure. More specifically, it can preferably be wound at least once, or a plurality of times if higher demands are made on the insulation. Production of preshaped half-shell portions in a sandwich structure is also a possible option.
In accordance with an added feature of the invention, the at least one metal sheet or foil at least at one end of the honeycomb body covers over an adjacent ceramic layer at the end. That provides for particularly effective protection, in particular from pulsating hot exhaust gases to be cleaned, which flow into the honeycomb body configuration, since they can no longer flow directly against the ceramic layer and thus erosion thereof is prevented.
In accordance with a concomitant feature of the invention, the metal sheets and the ceramic layers which are possibly connected thereto advantageously have a structuring, in particular a corrugation. That advantageously makes it possible for the metal sheets to be bent in the peripheral direction of the honeycomb body, using low forces.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a honeycomb body configuration with an intermediate layer containing at least one metal layer and a sandwich structure in particular for a honeycomb body configuration, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.